KR20100123599A - Metallic heat transfer tube - Google Patents

Abstract

PURPOSE: A metal-based heat exchanging pipe is provided to reduce the size of a liquefier by improving heat transmission on the inner side of the metal-based heat exchanging pipe. CONSTITUTION: A metal-based heat exchanger(1) includes a pipe wall(2) and a rib(3). The rib includes a rib bottom part(31), a rib lateral part(32), and a rib upper part(33). The rib is integrated with the external side of the pipe wall. The rib bottom part is radially protruded from the pipe wall. A part, which is composed of material protrusions(4), is arranged on the rib lateral part. The material protrusion includes a plurality of boundaries(41, 42).

Description

Metal Heat Transfer Tube {Metallic Heat Transfer Tube}

The present invention relates to a metal heat exchange tube according to the concept of claim 1.

Metal heat exchange tubes are used to condense liquids consisting of pure or mixed materials, especially on the outside of the tubes. Condensation is occurring in many fields such as freezing and heating and cooling as well as process and energy technologies. On the outside of the tube, steam consisting of pure or mixed materials is liquefied, and inside the tube, a multi-tube heat exchanger is frequently used in which brine or water is heated. Such a device is called a multi-tube condenser or a multi-tube liquefier.

Heat exchange tubes for shell and tube heat exchangers typically have at least one structured area and smooth ends and optionally smooth intermediate connections. The smooth terminal or central connection defines the structured region. Thus, if the outer diameter of the structured region is not large compared to the outer diameters of the smooth end and intermediate connections, the heat exchange tube can be installed without problems in the multi-tube heat exchanger. High efficiency pipes currently in use today have about four times the efficiency of smooth pipes of the same diameter.

Various forms are known for increasing heat transfer upon condensation outside the tube. Typically, ribs are formed on the outer surface of the tube. This rib formation primarily increases the surface area of the tube, causing condensation to occur more extensively. The formation of ribs from the wall material of the smooth tube is very advantageous for heat transfer because proper contact is made between the rib and the tube wall. It is called the rib tube which integrally rolled the tube which formed the rib through the shaping process from the wall material of a smooth tube.

Techniques for forming a notch on top of the ribs to further increase the surface area of the tube are known. This notched structure has a desirable effect on the condensation process. Techniques for forming notches on top of ribs are known, for example, from US 3,326,283 and US 4,660,630.

A rib structure having a rib density having a rib density of 30 to 45 ribs per inch is formed on the outer side of a rib tube for liquefiers recently commercialized. This corresponds to a rib pitch of about 0.85 to 0.56 mm. Such rib structures are shown for example in DE 44 04 357 C2, US 2008/0196776 A1, US 2007/0131396 A1 and CN 101004337 A. The improvement in performance through increased rib density is limited by the inundation effect seen in a shell and tube heat exchanger. If the distance between the ribs is small, the condensate overflows due to capillary action in the space between the ribs, and the channel between the ribs becomes smaller, which obstructs the flow of the condensate.

It is also known that structures can be further formed at rib side regions between the ribs at a constant rib density to improve the performance of the liquefaction tube. Such a structure can be formed on the rib side through the toothed disk. In this case, the material protrusion to be formed protrudes internally into the space formed between the adjacent ribs. Embodiments of this structure can be found in US 2008/0196876 A1, US 2007/0131396 A1 and CN 101004337 A. The patent document describes a material protrusion as a component having a planar interface. However, there is a disadvantage that the interface of the plane does not receive any force induced by the surface tension which causes the condensate formed in the plane to separate from the interface. The result is an undesirable liquid film that can continue to interfere with heat transfer.

It is an object of the present invention to provide a high efficiency heat exchanger tube for condensation of liquids outside the tube which can exhibit heat transfer and pressure drop on the same tube side and can be manufactured at the same manufacturing cost. In this case the mechanical stability of the tube is not impaired.

The invention is well represented through the features of claim 1. Other citation claims relate to advantageous and further embodiments of the invention.

The present invention has a tube wall, rib bottom, rib side and rib top, and having ribs integrally formed around the outside of the tube, wherein the rib bottom is substantially radially protruding from the tube wall and disposed laterally on the rib side. A component formed as a protrusion is further provided, and the material protrusion includes a heat exchange tube made of metal including a plurality of interfaces.

According to the invention, at least one of the interfaces of the at least one material protrusion is convexly curved.

The present invention relates to a structured tube having an increased heat transfer coefficient outside the tube. Because structuring often transfers the main component of thermodynamic resistance to the inside, the heat transfer coefficient inside must eventually increase. Increased heat transfer inside the tube usually results in an increase in pressure drop at the tube side.

The present invention begins with the integrally rolled rib tube comprising a pipe wall and ribs enclosed in a thread form on the outside of the tube. The ribs have rib bottoms, rib tops, and rib sides on both sides. The bottom of the rib protrudes substantially from the tube wall. The height of the rib is the distance measured from the pipe wall to the top of the rib, and is preferably 0.5 to 1.5 mm. The outer shape of the rib is concave and curved radially in the rib bottom region and the region of the rib side connected to the rib bottom. In the region of the rib top and the rib side connected to the rib top, the contour of the rib is curved convex in the radial direction. At approximately half of the rib height the convex bends are converted into concave bends. Condensate produced in the region of the convex bends is released by surface tension. The condensate gathers in the region of the concave bend to form water droplets.

Further components according to the invention are formed in the form of material projections laterally on the rib side. The material protrusion is formed from the material of the upper rib side, and similarly separates the material of the rib side using a tool at the rib side, but does not separate from the rib side. The material protrusion is firmly connected to the rib. In this connection position a concave edge is formed between the rib side and the material protrusion. The material protrusion extends substantially in the axial direction of the rib side in the space between the two ribs. The material protrusions can in particular be arranged approximately on half of the rib height. The material protrusion increases the surface area of the tube.

Opposite located material projections of adjacent ribs do not contact each other. For this purpose the axial extension of the material protrusion is slightly less than half the width of the space between the two ribs. For example, for a liquefied tube for coolant R134a or R123 the width between the two ribs is about 0.4 mm, and the axial extension of the material protrusion is less than 0.2 mm.

According to the invention, the material protrusion is defined by at least one convex curved surface. This convex shape improves the effect of the additional component. Surface tension causes the condensate to break away from the convex curve and move to the concave edge of the joint between the material protrusion and the rib side. Thus, a thin film of condensate is formed at the convexly curved interface of the material protrusion, thereby deteriorating heat resistance. The material protrusion is arranged in the region of the rib side where the convex bend shape of the rib is converted into the concave bend shape. Condensate from the upper region of the ribs and material protrusions meet at the connection and form water droplets at the concave bends of the ribs.

The additional structures provided laterally on the rib side described in US 2007/0131396 A1 and US 2008/0196876 A1 are planar components which do not have the advantageous properties mentioned above.

In particular, in relation to the effective heat transfer outside the tube, there is an advantage that the heat transfer inside the tube can be increased to significantly reduce the size of the liquefier. This reduces the manufacturing cost of the liquefier. In this case, according to the present invention, the liquefier can be manufactured without any adverse effect on the mechanical stability and the pressure drop of the tube. In addition, it is possible to reduce the required filling amount of the coolant, which occupies a non-negligible portion of the total device cost, such as the chlorine-free safety coolant which is mainly used recently. The potential risk can be further lowered by reducing the amount of toxic or combustible coolant used only in special cases.

In a preferred embodiment of the present invention, the local radius of curvature of the convex interface can be reduced with increasing distance from the rib side. The local radius of curvature may be defined as the radius of the oscillating circle at each point of the convex interface. The contact source is then located in a plane aligned perpendicular to the rib side. The boundary surface may be arbitrarily formed to change the local radius of curvature. When the interface is covered by the liquid film, a pressure gradient occurs in the liquid film due to the surface tension and the changed radius of curvature. Due to this pressure gradient, the liquid is released from the region having a small radius of curvature and moved to the region having a large radius of curvature. It is particularly advantageous for the local curvature radius of the interface of the material protrusions to be smaller as the distance from the rib side becomes greater. From the area of the material projection away from the rib side, condensate is particularly efficiently released and transported into the rib.

Preferably, the convexly curved interface may face away from the tube wall. In this case, the vapor condensed at the interface may be introduced without being disturbed.

In a preferred embodiment of the present invention, the bent portion of the interface can be convexly curved in a plane parallel to the rib side, in which case the bent portion of the convex interface is in a plane parallel to the rib side. The strength is higher than the bend of the convex interface. This allows the condensate to move more advantageously into the rib laterally from the top of the material projection.

The radius of the imaginary circle, expressed as the average radius of curvature of the convex interface, can be determined through measurement at three points. In a particularly advantageous embodiment, the radius of the imaginary circle is located in a cross section perpendicular to the tube circumferential direction and defined by P1, P2 and P3 and may be less than 1 mm. P1 is the point adjacent to the rib side at the convex interface of the material protrusion, P3 is the point farthest from the rib side at the convex interface of the material protrusion, and P2 is between P1 and P3 at the outline of the convex interface of the material protrusion. It is a waypoint. If the radius of curvature exceeds 1 mm, commonly used materials, such as coolants or hydrocarbon materials, may not achieve sufficiently large surface tensions against gravity and thus have a decisive effect on the transport of condensate.

Preferably, the convex interface of the material protrusion may extend outwardly with the convex bend through P3 furthest from the rib side in the top region. In this case, the top of the material protrusion is usually curved helically. By this structure, the space formed between the ribs can be adjusted to obtain a surface area for wider condensation even at the same rib spacing.

In a preferred embodiment of the invention, the material protrusions disposed on the rib side can be spaced apart in the circumferential direction. This configuration further forms the edge where condensation takes place. In addition, condensate collected on the rib side in the region between the two material protrusions can flow to the bottom of the rib.

In another preferred embodiment of the invention, the material protrusions disposed on the rib side are at the same distance in the circumferential direction and can be at least spaced apart. This structure provides sufficient space for condensate to collect on the rib side, allowing condensate movement.

Hereinafter, embodiments of the present invention will be described in detail with reference to the schematic drawings.
1 is a partial perspective view of a rib cut of a heat exchange tube with a material protrusion.
FIG. 2 is a detailed view of the material protrusion shown in FIG. 1 with a convexly curved interface. FIG.
3 is another detail view of a material protrusion with two convexly curved interfaces.
4 is another detail view of a material protrusion with a double convexly curved interface.
5 is another detail view of the material protrusion with an extension line passing the point furthest away from the rib side.
It is a partial perspective view which shows the outer side of a heat exchange tube cutting part.
It is a partial perspective view which shows the inner side of a heat exchange tube cutting part.
8 is a cross-sectional view of the heat exchange tube cutout.

Parts corresponding to each other in all drawings are denoted by the same reference numerals.

1 is a partial perspective view showing a rib cut part of a heat exchange tube 1 having three material protrusions 4. A portion of the rib 3 formed integrally with the tube outer 21 is shown. The rib 3 has a rib bottom 31, a rib side 32 and a rib top 33 attached to a tube wall not shown in FIG. 1. The rib 3 protrudes radially from the tube wall. The rib side 32 is additionally provided with a component formed as a material protrusion 4 laterally attached to the rib side 32. The material protrusion 4 comprises a plurality of interfaces 41, 42. In the illustrated embodiment, the three boundary surfaces 42 of the material protrusions 4 are convexly curved in a direction different from the tube wall. According to the invention, in principle, each material protrusion 4 may be provided with an interface 42 or a plurality of identical interface 42 with convex bends. The other non-convex interface 41 may be formed flat or concave. The material of the integrally formed material protrusions 4 is primarily the material of the rib side portion 32, and the grooves 34 are formed by the material movement during the manufacture of the heat exchange tube 1.

2 is a detailed view of the material protrusion 4 with the convexly curved interface 42. The other non-convex interface 41 is continuous in planar form. In the convex region, the condensate condensed from the gas phase is moved by the surface tension, so that the condensate may increase or accumulate in the planar surface region in the concave curved region.

The average bending radius RM of the convex interface 42 of the imaginary circle K is defined by three points P1, P2 and P3. The radius RM can be used as a characteristic measure of the degree of protrusion of the convex surface. P1 is the point adjacent to the rib side at the convex interface 42 of the material protrusion 4, P3 is the point farthest from the rib side at the convex interface 42 of the material protrusion 4, and P2 is the material It is an intermediate point between P1 and P3 at the outline of the convex interface 42 of the protrusion 4. In the typical structural size of heat exchange tubes of the present invention comprising integrally rolled ribs, the mean radius of curvature (RM) is typically in the range of micrometers or less.

Another detailed view of the material protrusion 4 with two convexly curved interfaces located opposite each other of the material protrusion 4 is shown in FIG. 3. This geometry allows the condensate to move effectively inside, starting from the top of the material protrusion 4 and in particular towards the rib side. The interface 42 along with the interface 41 may also include convex bends for more efficient condensate movement. Such an embodiment may require a high level of process technology when structuring the integrated rib and material protrusion 4.

Another detailed view of another advantageous embodiment, the material protrusion 4 shown in FIG. 4, embodies a convexly curved interface 42 and a planar side 41. At this time, the bent portion of the convex interface in a plane perpendicular to the rib side is greater in strength than the bent portion of the convex interface 42 in a plane parallel to the rib axis portion. This curved surface further facilitates the flow of condensate towards the rib side.

FIG. 5, showing yet another exemplary embodiment, is a detailed view of the material projection 4 with the extension line passing through P3 furthest away from the planar boundary 41 and the rib side. In this embodiment, the top SP of the material protrusion 4 is spirally rolled inward to the bottom of the rib. This arrangement can optionally form a space between the ribs to obtain another surface for condensation. The bending radius RM of the convex interface 42 of the imaginary circle K is again specified by P1, P2, and P3.

6 is a partial perspective view showing the outside of the heat exchange tube cut 1. Another partial perspective view of the inside of the heat exchange tube cut is shown in FIG. 7. The rib 3 is shown integrally formed on the tube outer side 21 and surrounding the tube axis A. The rib top 33 is away from the tube wall 2 and is connected to the tube wall at the rib bottom 31. The rib side portion 32 is formed with a material protrusion 4 attached laterally to the rib side portion 32. The interface 42 of the material protrusion 4 is convexly formed in a direction different from the tube wall 2. The other non-convex interface 41 is planar in the embodiment according to FIG. 6. In FIG. 7, the side boundary surface 41 is planar, and the side boundary surface 41 toward a pipe inside is concave. The integrally formed material protrusion 4 is formed primarily of the material of the rib side 32 and partially formed of the material of the region of the rib top 33 to form the groove 34. The material protrusions 4 arranged on the rib side 32 are at the same distance in the circumferential direction U and are spaced approximately by their width. The axial extensions of the material protrusions 4 are chosen to be less than half the width of the space between the two ribs 3 so that the oppositely positioned material protrusions of adjacent ribs do not contact each other. An inner rib 5 is arranged spirally inside the tube 22 to further increase heat transfer to the liquid inside the heat exchange tube 1 as compared to the smooth tube.

8 is a cross-sectional view of the heat exchange tube cut 1. Inside the tube 22 is a spiral inner rib 5. On the tube outer side 21, the ribs 3 are arranged perpendicular to the tube wall 2 in a regular arrangement, and the rib top 33 is slightly flattened. The interface 42 of the material protrusion 4 attached to the rib side 32 and facing away from the tube wall 2 is convex, and the interface 41 facing the tube inner 22 is concave. have. Oppositely located material projections of adjacent ribs 3 are not in contact. This configuration results in a sufficient space for conveying the collected condensate.

1 heat exchanger tube
2 pipe wall
21 outside the tube
22 inner tube
3 rib outside the pipe
31 rib bottom
32 rib side
33 rib top
34 home
4 Material protrusion
41 boundary
42 convex interface
5 rib inside the tube
Top of SP material protrusion
U tube circumferential direction
A tube axis
RM average curvature radius
K circle
P1, P2, P3 Points on Convex Interface

Claims (8)

It has a tube wall (2), rib bottom (31), rib side portion 32 and the rib top (33) and has a rib (3) integrally formed around the tube outer portion 21, the rib bottom (31) is the tube wall ( The rib side 32 is further provided with a component formed as a material protrusion 4 which extends substantially radially from 2), and the material protrusion 4 has a plurality of boundary surfaces 41 and 42. As a metal heat exchanger tube 1 comprising:
Metal heat exchange tube (1), characterized in that at least one of the interfaces (42) of the at least one material protrusion (4) is convexly curved. The metal heat exchange tube (1) according to claim 1, characterized in that the local radius of curvature of the convex interface (42) is reduced with increasing distance from the rib side (42). The metal heat exchanger tube (1) according to claim 1 or 2, characterized in that the convexly curved interface (42) of the material protrusion (4) faces away from the tube wall (2). The boundary surface 42 according to any one of claims 1 to 3, wherein the bent portion of the boundary surface 42 is convexly curved in a plane parallel to the rib side 32, and the boundary surface 42 is convex in a plane perpendicular to the rib side 32. The heat exchanger tube (1) made of metal, characterized in that the bent portion is higher than the bent portion of the convex interface (42) in a plane parallel to the rib side portion (42). The convex interface 42 of any one of claims 1 to 4, wherein the radius RM of the imaginary circle K is located at a cross section perpendicular to the tube circumferential direction U. At the point adjacent to the rib side 32 at P1, the convex interface 42 of the material protrusion 4 at the point furthest away from the rib side 32 at the outline of the convex boundary 42 of the material protrusion 4 A metal heat exchange tube (1), characterized by being less than 1 mm defined by P2, which is the intermediate point between P1 and P3. 6. The metal according to claim 5, wherein the convex interface 42 of the material protrusion 4 extends outwardly with the convex bend through P3 furthest from the rib side 32 in the region of the top SP. Heat exchanger tube (1). The metal heat exchange tube (1) according to any one of claims 1 to 6, wherein the material protrusions (4) arranged on the rib side portions (32) are spaced apart in the circumferential direction (U). 8. Metal heat exchange according to any one of the preceding claims, characterized in that the material projections (4) arranged on the rib side (32) are at the same distance in the circumferential direction (U) and at least spaced apart by the width thereof. Tube (1).

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